Electrolytic method and cell for the decomposition of water



A. T. STUART 1,941,816

ELECTROLYTIC METHOD AND CELL FOR THE DECOMPOSITION OF WATER Jan. 2,1934.

Filed'April 22, 1930 2 Sheets-Sheet 1 Jan. 2, 1934. A T. STUART1,941,316

ELECTROLYTIC METHOD AND CELL FOR THE DECOMPOSITION OF WATER Filed April22, 1930 2 Sheets-Sheet 2 Patented Jan. 2, 1934 UNITED STATESELECTROLYTIC METHOD AND CELL FOR THE DECOMPOSITION OF WATER AlexanderThomas Stuart, Toronto, Ontario, Canada Application April 22, 1930.Serial No. 446,311

12 Claims.

It is known that when certain acids and bases are dissolved in water forelectrolytic purposes, the resulting solution is a conductor ofelectricity, that it has the property of suffering chemicaldecomposition by the passage of a uni-directional electric current, thatsuch solutions are called electrolytes, and that the process ofdecomposition'is referred to as electrolysis.

It is also knownz-that the solution when electrolyzed is split into itsradicals which migrate towards the anodes and cathodes and which, ifthey do not interact with the water, are set free; that during thedecomposition of certain electrolytes hydrogen is liberated at thenegative pole and oxygen is liberated at the positive'pole of thecurrent.

It is also knownz-that one type of cell suitable for the electrolyticdecomposition of water comprises a plurality of anodes and cathodesalternately arranged and connected in parallel and pforous diaphragmsfor separating the anodic and cathodic products of the electrolysis anddividing the cell into a corresponding number of anode and cathodecompartments; that this type of cell is commonly referred to as the tankor separate unit type of cell to contradistinguish it from the commonlyknown filter press or bipolar type; that when the electrolyte isdecomposed the positive radicals accumulate at the cathodes and thenegative radicalsaccumulate at the anodes as the electrolysisprogresses; and that this accumulation is due to the ionic migration ofthe radicals under the influence of the electric current; that the ionicmigration towards the cathodes withdraws the positive radicals from theanolyte and concentrates them in the catholyte, thereby impoverishingthe electrolyte at the anodes and enriching it at the cathodes; that themigration towards the anodes withdraws the negative radicals from thecatholyte and concentrates them in the anolyte, thereby impoverishingthe electrolyte at the cathodes and enriching it at the anodes; that inboth cases the ionic migration creates an unbalanced condition of thestrength, or positive ion concentration of the electrolyte throughoutthe cell; that this unbalanced condition is partly but not whollycorrected by a backward diffusion of the electrolyte through thediaphragms; that without this backward diffusion a basic electrolytewould rapidly become, during the operation of the cell process, purewater at the anodes, and an acid electrolyte would rapidly become purewater at the cathodes; that it is only by the partial correctiveresulting from this backward difiusion trodes when suitable ducts areprovided for removing the electrolyte from the top of and out of. thecell and for returning it to the bottom of the cell after the offtake ofthe gases; that in the filter press type of cell this principle isutilized and that it is common practice with batteries of filter presscells to so remove the anolyte and catholyte from the top of each cellin the battery by a pair of ducts, one common to all the anolytecompartments and the other common to all the catholyte compartments ofall the cells; that the electrolyte from all the cells is led to anapparatus exterior of the cells for separating the gases and forremixing the anolyte and catholyte; that the remixed electrolyte is thenreturned to the several cells by a common duct; that, in thiscirculatory system, shunt currents follow the common ducts and generatehydrogen in the oxygen duct and oxygen in the hydrogen duct, therebydelivering impure gases at the ofitakes. It is also kn0wn:that,heretofore, in the operation of tank types of cells, no provision hasbeen made for a positive circulatory system within the cell itselfwhereby the anolyte and catholyte, free from gases, are returned fromthe top of the several electrode compartments to the bottom of the cell,and thoroughly mix before again being admittedto the various electrodecompartments. According to this invention the method is adapted to atank type of cell and is characterized by the electrolyte in each cellbeing unmixed with the electrolyte from the other cells and a positivecyclic circulation of the electrolyte within each cell createdformaintaining all the electrolyte therein at uniform normal strength; thiscyclic circulation being effected by collecting the electrolyte from thetop of the electrode compartments of one polarity; maintaining itsseparation from the electrolyte of the compartments of the otherpolarity; and returning itto the bottom of the same cell through achannel separate from the electrode compartments to V recirculatetherethrough. It is further characterized by regulating the speed of thecirculation for ensuring the offtake of pure gas.

Various methods and means may be devised for creating and maintainingthis cyclic circulation and intermixing the anolyte and catholyte duringthe cell operation without departing from the principle of theinvention. One method which I have satisfactorily employed consists ofproviding separate channels of circulation for the anolyte and catholytefrom the top of the anode and cathode compartments, respectively, to thebottom of the cell, and intimately mixing them to restore the normalstrength of the electrolyte before re-entering the several cellcompartments. Another method which I have satisfactorily employedconsists of a positive cyclic circulation of the anolyte from the anodecompartments into the cathode compartments and the catholyte from thecathode compartments into the anode compartments, when the gases havebeen separated from it, thereby utilizing the enriched electrolyte ofone set of compartments for restoring the impoverishedelectrolyte in theother set of compartments to substantially normal strength throughoutthe several cell compartments, and maintaining the electrolyte atsubstantially uniform strength throughout the cell.

In both of the above methods the speed of the circulation may beregulated by valves or dampers suitably installed in the cyclic system,to control the rate of movement of the electrolyte and prevent the gasbeing carried to the bottom of the cell during the circulation.

For an understanding of the invention reference'is to be had to thefollowing description and to the accompanying drawings, in which:

Fig. 1 represents a vertical section of an oxygenhydrogen cell showing apreferred method of elec trode assembly, this section being taken on theline BB, Fig. 2.

Fig. 2 is a vertical section on the line A-A, Fig. 1. I

'Figs. 3 and 4 are similar views to Figs. 1 and 2 of a modification ofthe cell, with the electrodes omitted.

Like characters of reference refer to like parts throughout thespecification and drawings.

The cell comprises a tank A, a plurality of electrodes numbered 1 to 5,inclusive, alternately arranged as cathodes and anodes, and porousdiaphragms D interposed between them for separating the oxygen andhydrogen liberated during the decomposition of the electrolyte. Anynumber of electrodes may be used and the general construction'andassembly of the electrodes and the interposed diaphragms hereinafterdescribed and shown in the accompanying drawings are similar to theelectrodes shown and described in my Letters Patent 'of the UnitedStates of America 1,597,553 dated August 24th, 1926, but any other typeof electrodes and'diaphragms suitable for oxygemhydrogen cells may beemployed.

Each electrode comprises a current feeder and a group of thin, narrowstrips, arranged vertically in substantially parallel planes,individually separated, and directly connected collectively with thecurrent feeder. The current feeders 16 of the odd numbered electrodesare connected with the negative pole of the current and consequently allthe odd numbered electrodes are cathodes. The current feeders 17 of theeven numbered electrodes are connected with the positive pole of thecurrent and consequently all the even numbered electrodes are anodes.The feeders. 16 and 1'7 are shown to be located above the strips butthey may be located below the strips at a position which will intercepttheir vertical axes. In the assembly of the cell the anodes arepositioned between the cathodes. The strips forming the electrodes areset edgewise towards each other with the surfaces of the electrodes inthe same direction as the circuit of the current across the interveningspaces or electrolytic gaps between the anodes and cathodes, and each ofthese gaps is of a width approximately equal to the thickness of thediaphragms.

Above and overhanging each cathode is a channelled hood 20, and securedto the perimeter of the entire group of hoods are four skirts or plates22 for suspending the hoods from the cover 22a of the cell. The skirts01' plates 22, together with the group of hoods 20, form a header 220above the electrodes. Interjacent the hoods 20 are openings 2217,located one above each anode, for the circulation of the anolyte andanodic products into the header. Surrounding each anode is a diaphragmD, which is of a tubular formation, open at the top and'bottom, andextends from the hoods 20 to below the bottom of the electrodes forseparating the anodic and cathodic products of the electrolysis. 'Eachdiaphragrn is secured to thecontiguous walls of two adjacent hoods 20and the thickness of the diaphragm corresponds to the widthofthe'electrolytic gaps between the anodes and cathodes. The diaphragmsdivide the cell into a plurality of al ternately arranged anode andcathode compartments, A and C, respectively, and in conjunction with thechannelled hoods maintains the separae tion of the anolyte and catholyteand the anodic and cathodic products in their respective coinpartments.The width of each electrolytic gap, by corresponding approximately tothethickness of the diaphragm, permits of the edges of the anodes andcathodes in the cell assembly being in contact, or substantially so,with the diaphragms. The current from the positive, 01? is distributeduniformly to all the anodes and flows outwardly from the edges of eachinterposed anode stripand across the electrolytic gaps to the edges ofthe corresponding interposed cathode strips, from the edges of which itflows inwardly. In this arrangement each strip'of each electrode has twoactive ed es forming re acting areas with currents of equal intensityflowing inopposite directions from the edges of eachinterposedelectrodewhereby equalquantities of gas are evolved at each edge of eachinterposed electrode. The maximum current intensity exists at the edgesand the minimum current intensity exists interiacent the edges and thisdifferential of intensity providesa path be; I

tween the edges of each strip for the unimpeded and rapid uplift'of theelectrolyte and gases, and reduces to a negligible amountrthe gasesinsuspension between the electrodes and adhering to the electrodes anddiaphragms and tends to prevent polarization of the cell. The oxygen andanolyte rise to the top ofthe anode compartments and pass through theopenings 221) into thejheader 22c formed by the skirts 22 andchannell'edhoods, and these skirts and hoods keep the' anolyte andoxygen separated from the catholyte and hydrogen. The hoods 20 extendlengthwise of the celland beyon d the ends of the header 220. Thecatholyte fills the cathode compartments andthe upper partof the cell,exterior of the header to within a few inches of the cell'cover. Thecathodic products rise through the cathode compartments to the hoods andare conducted by them to the ends of the cell, exterior of the header,from which they pass-tov .lects under the cell cover.

the hydrogen ofitake 23. .The catholyte circulates upwardly through thecathode compartments to the hoods, by which .itis deflected to-the endsand from the header passes down the tube 26 and structed with a rod orrods 31 extendingabove the cell cover and fitted with a lock nut or nuts32 by which it is adjusted. By completely closing the valve-or damperthe cyclic circulation of the anolyte can be arrested. By fully openingit a rapid circulation may be maintained, and the speed or rapidity ofcirculation can be regulated between these extremes by the adjustment ofthe valve or damper.

During the operation of the cell process the current circuiting from thefeeders 1'7 to the anodes activates the edges of those electrode stripsand results in the liberation of oxygen, which rises through the anodecompartments and passes into the header, from which it escapes throughthe oxygen offtake 27. The current circuits outwardly from the edges ofthe anode strips to the edges of the cathode strips, from which itcircuits inwardly and passes to the feeder 16. The hydrogen generated inthe cathode compartments passes upwardly to the hoods and is directed bythem to the ends of the cell, from which it escapes through the hydrogenofitalre 23. In Figs. 3 and 4 a positive circulation of the electrolyteis maintained by connecting the bottom of the tube 26 with a manifold50, and connecting the manifold with the bottom of each cathodecompartment by a pipe 51, so that the anolyte passing down the tube 26and through the manifold 50 will be compelled to pass into the cathodecompartments C. The tops of the cathode compartments C are connected bypipes 52 with a tube 53 provided with a hydrogen ofitake 54. The bottomof the tube 53 is connected to a manifold 55, which in turn is connectedby pipes 56 with the anode compartments A and the catholyte is thuscompelled to pass into the anode compartments. Controlling thecirculation through the pipes 52 is a valve or damper 5'7 similar to thevalve or damper 30 for the purpose of regulating the speed of thecirculation. By closing the dampers and thereby preventing circulation,the voltage of the cell immediately rises, with a consequent lowering ofthecell efficiency. By opening the damper the circulation is renewed,the voltage falls to normal, and the cell efficiency is restored.

Having thus fully described my invention, what I claim as new and desireto secure by Letters Patent is:

1. An electrolytic method for the decomposition of water which, inaddition to the electrolysis and ofitake of the gases, comprises apositive cyclic circulation of the electrolyte within the cell createdby returning the anolyte and catholyte, free of oxygen and hydrogen,from the top to the bottom of the cell, intermixing them for restoringthe electrolyte to and maintaining it at substantially uniform strengththroughout the alternately arranged as anodesand cathodes,

cell, and regulating the speed of the circulation for ensuring theofftake of pure gases. v

2. An electrolytic cell for the decomposition of water which comprises aplurality of electrodes 8 and porous'diaphragms interposed between themfor'dividing the cell into a corresponding num ber of anode and cathodecompartmentain combination with means within the cellseparate from theanode and cathode compartments for returning the anolyte and thecatholyte from the tops of the anode and cathode compartments,

respectively, to the bottom ofthe cell and inter- -mixing them below theelectrodes for maintaining the electrolyte at substantially the samestrength throughout the cell, and, means for controlling the speed. ofthe circulation through the cell. I

3. An electrolytic cell as claimed in claim 2 having means for thereturn of- ,the anolyte from all the anode compartments, and, othermeans for the return of the catholyte from all of the cathodecompartments to the bottom of the cell.

4. An electrolytic cell as claimed in claim 2 having means for thereturn of the anolyte from all the anode compartments, and other meansfor the return of the catholyte from all of the cathode compartments tothe bottom of the cell, and means for regulating the speed of thecirculation.

5. An electrolytic cell for the decomposition of water including aplurality of electrodes alternately arranged as anodes and cathodes, andporous diaphragms interposed between them for dividing the cell into acorresponding number of anode and cathode compartments, in combinationwith means for creating a cyclic circulation of the electrolyte byreturning the anolyte and catholyte from the top of the anode andcathode compartments to the bottom of the cell and intermixing thembelow the electrodes for maintaining the electrolyte at substantiallythe same strength throughout the cell, which comprises a header locatedabove the electrodes in circulation with all the anode compartments, anda duct extending from the header for the return of the anolyte to thebottom of the cell, and means for regulating the speed of thecirculation for ensuring the ofitake of pure gas.

6. An electrolytic cell as claimed in claim 5 having valves forcontrolling the flow from the header through the duct and regulating thespeed of the circulation of the anolyte.

7. An electrolytic method for the decomposition of water in a tank typecell characterized by a positive cyclic circulation of the electrolytewithin each cell for maintaining all the electrolyte therein at uniformnormal strength effected by collecting the electrolyte from the top ofthe electrode compartments of one polarity; maintaining its separationfrom the electrolyte of the compartments of the other polarity andreturning it to the bottom of the same cell separately from theelectrode compartments, mixing it with the electrolyte from theelectrode compartments of the other polarity and then recirculating themixed electrolyte through the electrode compartments.

8. An electrolytic method for the decomposition of water in a tank typecell characterized by a positive cyclic circulation of the electrolytewithin each cell for maintaining all the electrolyte therein at uniformnormal strength effected. by collecting the electrolyte from the top ofthe electrode compartmentsof one polarity; maintaining its'separationfrom the electrolyte of the compartments of the other polarity and re-'turning it to the bottom of thesame cell to reof the circulationforensuring the'offtake of pure circulate therethrough, and regulating thespeed -9. An electrolytic method for the decomposiing the enrichedelectrolyte of one set of 00mpartments for restoring the impoverishedelectrol'yte of the other set of compartments to substantially normalstrengh throughout the cell.

10. The electrolytic-method for the decompm sition of water as claimedinclaim 9 inwhich the electrolyte from both sets of compartments isreturned separately to the bottom of the cell through diflerentchannels.

11. An electrolytic method for the decomposition of water as claimed inclaim 9 in which the speed of the circulation is regulated to controlthe rate of movement for the return of the electrolyte from the top tothe bottom of the cell.

12. An electrolytic method for the decomposition of water as claimed inclaim -'I in which the speed of the circulation is regulated forensuring the oiftake of pure'gases by preventing them being carried insuspension in the anolyteand catholyte returning from the anode andcathode compartments to the bottom of the cell.

ALEXANDER '1'. STUART.

